European Lancelet

The European lancelet (Branchiostoma lanceolatum), European amphioxus, Mediterranean lancelet, or Mediterranean amphioxus is a lancelet in the subphylum Cephalochordata.

Etymology

Coming soon

Physical Appearance

The elongated body of the European lancelet is pointed at both ends and flattened laterally. The notochord, a stiffening rod of densely packed cells, runs the length of the body. In contrast to vertebrates, the notochord remains in the adult as a simple dorsal neural tube that has a somewhat thicker anterior portion (the cerebral vesicle). A nerve chord with a single frontal eye is located above it. A tuft of 20 or 30 cirri, or thin sensory appendages, encircles the mouth, which is located on the bottom of the body.

From the mouth to the anus, in front of the tail, the gut runs directly beneath the notochord. The pointed tail is surrounded by a vertical fin that resembles a flap. Segmented gonads are located directly behind the gill slits in the midregion, where gas exchange occurs when water flows through them. Because the animal is semi-transparent and pearly white, the internal organs can be seen from the outside. In appearance, it resembles a "primitive imitive fish." Its maximum length is 6 cm (2.5 in).

Abilities

Toll-like receptors (TLRs) are essential mediators of inflammatory pathways that initiate an innate immune response in chordates. Data show that amphioxus TLRs have a similar framework in terms of protein structure, as well as similar properties to invertebrate TLRs, despite their heritage. In short, TLRS in amphioxus suggest a paraphyletic link to the vertebrate TLR lineage. The mitochondrial genome of Branchiostoma lanceolatum has been sequenced, and the species serves as a model organism for studying the development of vertebrates. The way the coding genes and the two rRNA genes are organized is the same as the organizational method used by the sea lamprey (Petromyzon marinus). These data, among others, suggest a close relationship between Branchiostoma lanceolatum and the vertebrates.

Ecology

In the North Sea, breeding takes place in June and July. The mature adult European lancelet, aged 2 to 3 years, congregates in masses on the seafloor. Individuals are either male or female and spawn once a year. The eggs are laid, and fertilization takes place externally. The early larval stages take place in the substrate, but a little later, the larvae become pelagic. They are elongated and flattened laterally and have a swollen region around the gill slits. These slits number 6 to 19, the number increasing as the larva passes through its various stages. The larvae have a vertical daily migration. Each evening they rise to near the surface of the sea, and in the morning they sink through the water column, feeding on phytoplankton, copepods, and detritus as they descend. While in these surface waters, they drift with the current. The larval stage lasts for up to 200 days.

Behavior

Shy.

Distribution and Habitat

The European lancelet is found in shallow seas in the north-east Atlantic Ocean, from 67°N in Norway south to the Mediterranean Sea and east to the Black Sea. Its range has expanded through the Suez Canal to the northerly parts of the Indian Ocean and the coasts of East Africa. It burrows in soft substrates such as sand, gravel, and shell fragments and is quite particular as to the size of the particles. It occurs from the low tide mark down to about 40 meters (130 ft).

Movement Pattern: Random
Individual Type: Solo
Population Trend: none
Population: ???
Locomotion: Aquatic
Habitat: Warm Littoral; Cold Littoral; Warm Intertidal; Cold Intertidal; Neritic Zone (Warm); Neritic Zone (Cold); Pelagic Zone (Warm); Pelagic Zone (Cold); Benthic Zone; Abyssal Zone; Hadal Zone; Hydrothermal Vent.
Earth:
- Extant: Albania; Algeria; Comoros; Croatia; Denmark; Egypt; Finland; France; Greece; Iceland; India; Iran; Iraq; Ireland; Israel; Italy; Jordan; Kuwait; Madagascar; Maldives; Mauritius; Morocco; Norway; Palestine; Portugal; Qatar; Saudi Arabia; Seychelles; Sri Lanka; Spain; Sweden; Tunisia; Turkiye; United Arab Emirates; United Kingdom
Berbania/Hirawhassa: none
Reinachos/Ityosel: none
Thatrollwa: none
Sawintir: none
Agarathos: none